The major aim of this proposed research is to improve our understanding of the mechanism responsible for the hyperacute rejection of kidney transplants in recipients without detectable antibodies directed against peripheral lymphocytes. For this purpose we expect to develop a sensitive complement-dependent serologic assay system utilizing cultured human lymphoid cells as targets to detect humoral sensitization in sera from prospective recipients of transplants and from patients during their post transplant periods. Expression of antigens reactive with such antibodies will be quantitated during the growth cycles of cultured cells, after expression of EB virus related antigens and on peripheral lymphocytes treated with proteolytic enzymes. The specificity, lytic efficiency, pathway of complement activation and immunoglobulin class of these antibodies to cultured human lymphoid cells will be characterized and compared to those of antibodies cytolytic to peripheral lymphocytes. Variattons in the properties of these antibodies will be correlated with the clinical course of the kidney transplant to determine any prognostic value. Antibodies reactive with cultured human lymphoid cells, the corresponding antigens solubilized from cells and the antigen-antibody complexes will be evaluated for their effects on both the recognition and the effector phases of the cellular immune response by using several in vitro tests. The presence of antibodies to cultured human lymphoid cells will be correlated with the HL-A phenotype of serum donors to ascertain any linkage between this humoral immune response and presence of certain histocompatability antigens. The results of these tests as well as the serological characteristics of humoral antibodies will be evaluated to explore: 1) methods of detecting or evaluating potential transplant rejection, 2) utilization of our assays in defining the relationship between recipient and kidney transplant.